The present invention relates to clamp rings, and more particularly to devices and methods for automated production of clamp rings.
Clamp rings have become a popular device for creating wreaths and similar items. As is well known, clamp rings typically have a spine in the shape of a ring to which are attached a number of spaced clamps used for holding material (e.g., boughs, decorations, and the like) to the ring. The spine and clamps are usually made from wire, with the spine wire normally being of a heavier gauge than the wire used to make the clamps (often called xe2x80x9cribxe2x80x9d wire). The spine therefore provides sufficient strength and rigidity to the wreath while the clamps can be bent around material to be held to the spine. The clamps can be bent by hand, by a pair of pliers or other hand tool, or by a machine adapted for bending the clamps about the material to be held. Although a number of different clamp shapes exist, clamps are typically U-shaped with two legs and a back attached to the spine. Typically, the clamps are welded to the spine in any conventional manner.
As a result of the popularity of the above-described wire clamp ring, various devices and methods have been developed for producing such clamp rings more rapidly and reliably. One such device is disclosed in U.S. Pat. No. 5,829,490 issued to Kilbane. In the Kilbane device, a spine wire and a rib wire are fed perpendicularly to one another between male and female dies and adjacent to an anode in the male die. By actuation of a pneumatic cylinder, the female die is moved toward the male die, thereby cutting the rib wire and bending the rib wire into a U-shape between the dies to form a rib (a clamp) of the clamp ring. After this movement, a second pneumatic cylinder is actuated to bring a welding electrode into contact with the crossed rib and spine wires. An electrical current passed through the electrodes and wires then welds the rib wire to the spine wire. Next, both pneumatic cylinders retract to permit the spine wire and rib to be moved out from between the dies in preparation for the next rib forming and welding cycle. Because the spine wire fed to the dies is bent in an arc, a ring is eventually produced having the desired spaced-apart clamps welded thereto. After the ring is completed, the spine wire is cut and the wire clamp ring can be completed by welding the ends of the ring together.
Although conventional clamp ring manufacturing devices represent a significant improvement over manual assembly of clamp rings, they are not without their shortcomings. Significant factors in the success of clamp ring manufacturing device designs are the speed at which the devices can operate, the reliability of the ring-to-clamp connections made, the lifespan of the device, the manufacturing and maintenance costs of the device, and the ability of the device to produce different types of clamp rings. However, conventional clamp ring manufacturing devices fail to perform well in the majority of these areas.
For example, a common problem in the production of ring clamps is poor rib wire to spine wire attachment. In many instances, a rib falls off of the spine immediately after the welding operation is performed or soon thereafter. However, more serious problems can occur when the rib is partially attached to the spine and passes to the end user, who breaks the clamp off of the spine while attempting to manipulate the clamp. The partially-finished wreath is typically thrown away without disassembly, representing a waste of end user material and time. Even a small number of poor welds can frustrate the customer enough to return an entire shipment of clamp rings to the manufacturer. Therefore, the need to consistently and strongly attach clamps to the spine of the clamp ring is highly important.
The need for rapidly producing ring clamps is often at odds with the need to produce quality clamp welds. Specifically, weld quality in many prior art machines can drop significantly at faster machine speeds.
A source of clamp-to-spine attachment problems is the need to precisely control welding variables such as temperature, pressure, and welding time. In the conventional electrical welding systems commonly used in clamp ring manufacturing devices, the pressure at which the spine and rib wires are held against the electricity-supplying electrodes is important to creating a proper weld. However, because the actuator used must be strong enough to bend and form rib wires into clamps (e.g., into U-shaped clamps), the ability to precisely control actuator force is at odds with the use of larger, more powerful, and less precise actuators. The result is either less control over welding pressure or the inclusion of a second more precisely controllable actuator such as that employed in the device disclosed in the Kilbane patent mentioned above. Less control over welding pressure can result in poorer welds, while the addition of a second actuator adds complexity and expense to the device.
Due to the cyclical motion of clamp ring manufacturing machines and their often constant operation, the chances of machine breakdown can be high. As noted in the Kilbane patent mentioned above, repeated torque loads can be imparted to the actuation device and can cause premature failure of the actuation device. Structure added to counteract destructive loading can add significant complexity and expense to the machine and/or can negatively affect overall system speed and performance in other ways.
A desirable feature of clamp ring manufacturing machines is the ability to manufacture rings having different sizes. Although some existing machines can produce such rings, they do so by employing complex mechanisms that can be difficult to adjust and are expensive to manufacture and maintain. For example, when the desired radius of a spine wire is changed by changing the relative positions of upstream wire forming rollers, the feed path of the wire is usually also changed. Because the spine wire must still be fed between the dies as described above, some conventional clamp ring manufacturing machines employ elaborate adjustment and positioning mechanisms for re-positioning the spine wire through the dies. These mechanisms are often difficult to manipulate and consume valuable user time that could otherwise be used for making ring clamps.
Although the above discussion and the following description and claims is with reference to ring clamps, it should be noted that the present invention is relevant to the production of similar products that may or may not be in the form of a ring (and can be straight or take any other shape desired). The present invention lies not just in the ability to manufacture ring clamps, but more broadly in a machine and method for producing elements having a spine of any shape to which is connected one or more ribs of any shape used as clamps for holding any material to the spine. Therefore, the term xe2x80x9cclamp ringxe2x80x9d as used herein and in the appended claims is intended to encompass similar devices having other shapesxe2x80x94whether resembling a ring or not. The connection between the spine and ribs is typically a welded connection of metal wires, but can be a brazed, soldered, glued, melded, or other connection of elongated elements made from any resilient material (e.g., plastic, composites, and the like) having any cross-section (e.g., round, oval, flat or ribbon-like, rectangular, square, polygonal, and the like) and size performing similar functions to the spine and ribs described above. Any material can be held to the spine, the material selected depending upon the application intended for the manufactured elements. Most commonly, the application is in making wreaths as will be described hereinafter by way of illustration only, wherein the material includes branches and/or other foliage. However, any other material can be used as desired.
In light of the problems and limitations of the prior art described above, a need exists for a clamp ring manufacturing apparatus and method in which ring clamps can be quickly produced with reliable, consistent and strong clamp-to-spine connections, the clamp ring size can be easily and readily changed, and in which the clamp ring manufacturing apparatus is simple, relatively inexpensive to manufacture, assemble, and maintain, and is not susceptible to fatigue from extended operation and cyclical forces. Each preferred embodiment of the present invention achieves one or more of these results.
Preferred embodiments of the present invention employ a clamp ring apparatus having an upper die assembly with an upper die, a lower die assembly with a lower die, an actuator for bringing the upper die assembly and the lower die assembly together (and more preferably for moving the upper die assembly toward and away from a stationary lower die assembly), a leg deflection element for offsetting legs of clamps formed by the apparatus, and a spring for controlling welding pressure on the wires formed to make the clamp rings. Spine and rib wires are fed into the apparatus from respective wire supplies, and are preferably brought into overlapping relationship between the upper and lower die assemblies. Wire guides on either of the die assemblies can be used to guide the wires to a position between the upper and lower dies. In some preferred embodiments, electrodes are located at or near this position. In one highly preferred embodiment, a lower electrode is received within a lower male die and an upper electrode is located between elements defining an upper female die. Preferably, each electrode is releasably held within its respective die assembly by a single fastener, thereby enabling fast and convenient electrode removal and replacement.
In contrast to some conventional devices, a single actuator is preferably employed both to move the die assembly to which it is attached and to move the electrode associated with that die assembly into welding position (the electrode preferably being secured in place upon the die assembly). The spring is preferably used to help control the force exerted upon the crossed wires between the dies, and preferably provides a constant die-separating spring force over a range of die positions. Improved welding pressure control enabled by the use of the spring provides for a greater ability to employ one actuator to form clamps and to press the wires together (thereby reducing apparatus complexity and increasing apparatus reliability), and also results in stronger, more reliable, and more repeatable welds.
Where used, the leg deflection element is preferably mounted in one of the die assemblies adjacent to the dies. In one preferred embodiment, the leg deflection element is located adjacent to a male die on one of the die assemblies. The leg deflection element has a leg deflection surface against which the leg of a clamp being formed is pressed and passes, thereby offsetting the leg with respect to some or all of the rest of the clamp. Preferably, the leg leaves contact with the leg deflection surface before the clamp is fully formed. Therefore, undesirable forces which can be generated by leg deflection in the later stages of a clamp""s formation are avoided. This helps to prolong the life of the actuator.
A wire guiding mechanism can be used to shape the spine wire to a desired radius of curvature, and preferably employs adjustable elements upon which wire forming rollers are mounted. Preferably, each adjustable element can be releasably secured in place by one or more releasable fasteners and in some highly preferred embodiments can be precisely adjusted to different positions by one or more positioning screws. The positions of the forming rollers with respect to the dies and with respect to each other can thereby be quickly and easily changed to change the shape of the spine wire.
Some preferred embodiments of the present invention also employ a cutoff lever assembly used to cut off the spine wire after a clamp ring has been completed. Preferably, the cutoff lever is pivotably mounted to one die assembly and is actuated by being pressed by a positionable block connected to the other die assembly. The block is preferably connected to and positionable by an actuator which, when actuated for cutting the spine wire, moves adjacent to the cutoff lever and is pressed against the cutoff lever when the movable die assembly is actuated to form the next clamp. In some embodiments, the weight of the die assembly assists in cutting the spine wire with the cutoff lever, thereby reducing the power requirements of the apparatus.
Preferably, various elements in the die assemblies are adjustably mounted to increase the flexibility of the apparatus. For example, the wire guides can be adjustably mounted to change the angular relationship of the wires being attached, the leg deflection element can be adjustably mounted to change the amount (if any) of clamp leg deflection, and the wire forming rollers and the wire shaping mechanism can be adjustably mounted to change the shape of the spine wire.
To better control die assembly movement, to protect the actuator against undesirable lateral and torque forces, and to enable both die assemblies to be removed and replaced without disturbing their positions relative to one another, die post and collar sets can be attached to the die assemblies. Specifically, die posts on one die assembly can be telescopingly received within collars on the opposite die assembly.